The reason? Apparently T-Mobile "did not approve" of a company called EZ Texting, which does business with a website, WeedMaps.com, that provides information on the location of legal medical marijuana dispensaries in California.

On Friday, EZ Texting sued T-Mobile in the U.S. District Court in New York City. EZ Texting says that on Sept. 10th, T-Mobile began "unlawful blocking" of its 313131 text service, which it offers to business and non-profits to help get their message to the public.

"T-Mobile has cut off my code and put my business in jeopardy," Shane Neman, CEO of EZ Texting told DailyFinance. "There's nothing illegal about knowing about legal dispensaries in the states they are legal in."

Founded in 2006, New York-based EZ Texting has 10,000 small business and non-profit customers all over the country that use its SMS platform to send content to users. "None of our customers can send texts through 313131 on T-Mobile," Nemen says. "None of the other carriers are blocking us."

A Growing Problem

"EZ Texting is being irreparably damaged in its business because of the blocking by T-Mobile," Neman said in a declaration to the court. "The ability to exchange text messages with all cell phone users is vital to EZ Texting's business."

The case highlights the growing tension between new startups like ChaCha, 4Info and EZ Texting that use text messages to deliver content to users and the mobile carriers on whose networks those texts travel. T-Mobile is a division of German mobile giant Deutsche Telekom (DTEGY).

"EZ Texting has a rigorous screening process to ensure that the businesses and non-profits that use EZ Texting to send text messages are doing so in compliance with all applicable laws and regulations," Neman said.

The company claims T-Mobile began blocking it after learning that a company that provides information about medical marijuana dispensaries in California was using the service. It says it was informed by OpenMarket -- the same aggregator as in the ChaCha situation -- that T-Mobile had found the site to be objectionable, hence the blocking.

Aggregators are middlemen that stand between publishers like ChaCha and EZ Texting, as well as Twitter, Facebook and ESPN, and the mobile subscribers they send content to.

Neman said that while the commercial aspect of T-Mobile's actions are important, there is a broader issue.

"Consumers should have the right to text with whomever they want," he says. "They have as much of a right to make text messages as they do phone calls. If T-Mobile is blocking legal medical marijuana texts, what's next, gay marriage, the Tea Party?" Neman says.

Gigi B. Sohn, president and co-founder of Public Knowledge, a DC-based advocacy group, blasted T-Mobile for blocking a legal service.

"This case is yet another example of a totally arbitrary decision by a carrier to block text message calls between consumers and organizations they want to communicate with," Sohn said in a statement. "The FCC should put a fast end to this blocking by issuing the ruling we asked them for three years ago. EZ Texting and other companies should be able to focus on growing their business rather than filing lawsuits to prevent blocking."

As new businesses spring up that rely on text messaging to serve content to customers, their relationship with the big mobile carriers will only get more acrimonious. T-Mobile's battles with ChaCha, 4Info and EZ Texting are signs of things to come.